U.S. patent application number 09/260209 was filed with the patent office on 2002-05-23 for pressure vessel with composite sleeve.
Invention is credited to HARGETT, WYATT PRICE JR., KING, EDWARD EARL.
Application Number | 20020061372 09/260209 |
Document ID | / |
Family ID | 22988226 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020061372 |
Kind Code |
A1 |
HARGETT, WYATT PRICE JR. ;
et al. |
May 23, 2002 |
PRESSURE VESSEL WITH COMPOSITE SLEEVE
Abstract
A self sealing vessel assembly for high pressure microwave
assisted chemistry is disclosed. The vessel assembly includes a
polymeric cylinder and a circular polymeric cap for the cylinder,
the cylinder being closed at one end and open at the other end to
receive the cap. The open end of the cylinder has a lip that is
beveled inwardly from the open end, and the circular polymeric cap
has a beveled lower edge that engages the beveled lip when the cap
is place upon the polymericcylinder. For high pressure
applications, a choke cylinder depends from the beveled lower edge
of the cap, and has an outer diameter substantially the same as the
inner diameter of the polymeric cylinder so that the choke provides
a self sealing mechanism for the cylinder as pressure from a
chemical reaction increases within the cylinder. A composite sleeve
surrounds the polymeric cylinder, and includes at least one wound
fabric layer in which the winding is selected from the group
consisting of filaments and yarns. A supporting frame extends along
the cylinder and across the lid and across the closed end of the
cylinder, and prevents the lid from being displaced from the
cylinder when pressure is generated inside of the vessel.
Inventors: |
HARGETT, WYATT PRICE JR.;
(MATTHEWS, NC) ; KING, EDWARD EARL; (CHARLOTTE,
NC) |
Correspondence
Address: |
SUMMA & ALLAN, P.A.
11610 NORTH COMMUNITY HOUSE ROAD
SUITE 200
CHARLOTTE
NC
28277
US
|
Family ID: |
22988226 |
Appl. No.: |
09/260209 |
Filed: |
March 1, 1999 |
Current U.S.
Class: |
428/36.3 |
Current CPC
Class: |
Y10T 428/131 20150115;
B01J 19/02 20130101; F16J 13/02 20130101; H05B 6/806 20130101; Y10T
428/1369 20150115; Y10T 428/1321 20150115; B01J 19/0073 20130101;
B01J 2219/1209 20130101; H05B 6/6408 20130101; Y10T 428/1314
20150115; B01J 2219/0295 20130101; G01N 2035/00405 20130101; B01J
19/126 20130101; B01J 2219/1215 20130101; Y10T 428/1366 20150115;
B01J 3/048 20130101; B01J 2219/0245 20130101; B01J 2219/1218
20130101; Y10T 428/139 20150115; Y10T 428/1393 20150115; G01N 1/44
20130101 |
Class at
Publication: |
428/36.3 |
International
Class: |
B32B 001/02 |
Claims
That which is claimed is:
1. A protective composite sleeve material for a microwave reaction
vessel, said sleeve material comprising a microwave-transparent
wound layer fixed with a microwave transparent structural medium,
said wound layer being selected from the group consisting of
filaments and yarns.
2. A composite sleeve material according to claim 1 wherein said
structural medium is a first polymer layer on one surface of said
wound layer.
3. A composite sleeve material according to claim 2 further
comprising a chemically-inert inner liner on the opposite surface
of said layer from said first structural polymer.
4. A composite sleeve material according to claim 3 and further
comprising a chemically inert outer liner on said first structural
polymer.
5. A composite sleeve material according to claim 4 wherein said
first structural polymer comprises a polyimide resin.
6. A composite sleeve material according to claim 5 wherein said
inner and outer liners are tetrafluoroethylene polymer.
7. A composite sleeve material according to claim 4 and further
comprising at least one additional textile layer and one additional
structural polymer layer between said first structural polymer
layer and said inert outer liner.
8. A composite sleeve material according to claim 7 wherein said
additional textile layer is selected from the group consisting of
wound filaments, wound yarns, woven fabric, braided fabric,
nonwoven fabric, and knitted fabric.
9. A protective composite sleeve for a microwave transparent
vessel, said sleeve comprising: a microwave transparent inner
cylindrical polymeric layer; a first microwave transparent wound
layer adjacent to and concentric with said inner polymeric layer in
which said winding is selected from the group consisting of
filaments and yarns; and a microwave transparent outer polymeric
layer.
10. A composite sleeve according to claim 9 and further comprising
a structural polymer layer between said wound layer and said
polymeric layer.
11. A composite sleeve according to claim 10 wherein said
structural polymer layer comprises an engineering resin.
12. A composite sleeve according to claim 11 wherein said
engineering resin is a polyimide.
13. A composite sleeve according to claim 10 further comprising a
plurality of pairs of adjacent concentric layers of structural
polymer and textiles between said inner and outer polymeric
layers.
14. A composite sleeve according to claim 13 wherein said textile
layers in said pairs are selected from the group consisting of
woven fabrics, braided fabrics, nonwoven fabrics, and knitted
fabrics.
15. A composite sleeve according to claim 13 wherein said textile
layers in said pairs comprise a winding selected from the group
consisting of filaments and yarns.
16. A composite sleeve according to claim 9 wherein said inner and
outer polymer layers comprise a tetrafluoroethylene polymer.
17. A self sealing vessel assembly for high pressure microwave
assisted chemistry, said vessel assembly comprising: a polymeric
reaction cylinder and a circular polymeric cap for said cylinder;
said cylinder being closed at one end and open at the other end to
receive said cap; said open end of said cylinder comprising a lip
that is beveled inwardly from said open end; said circular
polymeric cap having a beveled lower edge that engages said beveled
lip when said cap is place upon said polymeric cylinder; and a
choke cylinder depending from said beveled lower edge of said cap,
said choke cylinder having an outer diameter substantially the same
as the inner diameter of said polymeric cylinder so that said choke
provides a self sealing mechanism for said cylinder as pressure
from a chemical reaction increases within said cylinder.
18. A vessel assembly according to claim 17 wherein said cap and
said cylinder both comprise fluorinated hydrocarbons.
19. A vessel assembly according to claim 17 further comprising a
composite sleeve surrounding said polymeric cylinder, said
composite sleeve including at least one wound layer in which the
winding is selected from the group consisting of filaments and
yarns.
20. A vessel assembly according to claim 17 and further comprising
a supporting frame that extends along said cylinder and across said
and across said closed end of said cylinder for preventing said lid
from being displaced from said cylinder when pressure is generated
inside of said vessel.
21. A vessel assembly according to claim 20 wherein said frame
comprises an adjustable tightening means that urges said lid
against said cylinder.
22. A vessel assembly according to claim 21 wherein said tightening
means comprises: a threaded opening in said frame; and a bolt in
said threaded opening.
23. A self sealing vessel assembly for high pressure microwave
assisted chemistry, said vessel assembly comprising: a polymeric
cylinder and a circular polymeric cap for said cylinder; said
cylinder being closed at one end and open at the other end to
receive said cap; said open end of said cylinder comprising a lip
that is beveled inwardly from said open end; said circular
polymeric cap having a beveled lower edge that engages said beveled
lip when said cap is place upon said polymeric cylinder; a
composite sleeve surrounding said polymeric cylinder, said
composite sleeve including at least one wound layer in which the
winding is selected from the group consisting of filaments and
yarns; and a supporting frame that extends along said cylinder and
across said lid and across said closed end of said cylinder for
preventing said lid from being displaced from said cylinder when
pressure is generated inside of said vessel.
24. A vessel assembly according to claim 23 and further comprising
a choke cylinder depending from said beveled lower edge of said
cap, said choke cylinder having an outer diameter substantially the
same as the inner diameter of said polymeric cylinder so that said
choke provides a self sealing mechanism for said cylinder as
pressure from a chemical reaction increases within said
cylinder.
25. A vessel assembly according to claim 23 wherein said frame
comprises: a threaded opening in said frame adjacent said cap; and
a bolt in said threaded opening that bears on said cap when
tightened in said threaded opening.
26. A vessel assembly according to claim 23 wherein said cap and
said cylinder both comprise fluorinated hydrocarbons.
27. A vessel assembly according to claim 23 wherein said composite
sleeve comprises: a microwave transparent inner cylindrical
polymeric layer; a first microwave transparent wound layer adjacent
to and concentric with said inner polymeric layer in which said
winding is selected from the group consisting of filaments and
yarns; a structural polymer layer between on said wound layer; and
a microwave transparent outer polymeric layer on said structural
polymer layer.
28. A composite sleeve according to claim 27 comprising a plurality
of pairs of adjacent concentric layers of structural polymer and
textiles between said first wound layer and said outer polymeric
layer.
29. A composite sleeve according to claim 28 wherein said textile
layers in said pairs are selected from the group consisting of
woven fabrics, braided fabrics, nonwoven fabrics, and knitted
fabrics.
30. A composite sleeve according to claim 28 wherein said textile
layers in said pairs comprise a winding selected from the group
consisting of filaments and yarns.
31. A composite sleeve according to claim 27 wherein said inner and
outer polymer layers comprise a tetrafluoroethylene polymer.
32. A vessel assembly according to claim 23 wherein said supporting
frame is flexible under a predetermined force exerted by pressure
inside said cylinder and against said cap, so that the flexing of
said frame at said pressure allows said cap to disengage from said
cylinder and release the pressure inside.
33. A system for microwave assisted chemistry comprising: a source
of microwave radiation; a cavity in microwave communication with
said source; and a plurality of vessels according to claim 23 in
said cavity.
34. A system according to claim 33 wherein said source is selected
from the group consisting of magnetrons, klystrons, solid state
devices, and switching power supplies.
35. A system according to claim 33 and further comprising a
waveguide between said source and said cavity.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to microwave assisted
chemistry, and in particular relates to a reaction vessel structure
that can withstand high pressures without catastrophic failure.
BACKGROUND OF THE INVENTION
[0002] Microwave assisted chemistry refers to the use of microwaves
to initiate or accelerate chemical reactions. Microwave assisted
chemistry is particularly useful in heating materials that are
responsive to microwave radiation because under most circumstances,
the resulting heating takes place much more rapidly than it would
if the reactions were initiated or accelerated using more
conventional heating techniques such as convection or conduction
heating.
[0003] Microwave assisted chemistry can be used in a variety of
chemical processes including moisture determination, ashing,
digestion, extraction, and others. Under some circumstances, these
various techniques are preferably or necessarily carried out in
sealed vessels which, because of the generation or expansion of
gases inside, must be able to withstand high pressures.
[0004] Accordingly, a number of pressure vessels have been
developed that are suitable for high-pressure microwave assisted
chemistry. Such vessels are typically formed of microwave
transparent materials that offer the structural capabilities
required to withstand such high pressures. High-strength polymers
are exemplary of such materials and offer the required microwave
transparency and resistance to chemical attack. Such materials tend
to be brittle, however, so that failure under pressure tends to
destroy the vessel quickly and release its contents suddenly.
[0005] One recent advance in the construction of such vessels has
been to use a composite sleeve as one of the outer portions of the
reaction vessel. The composite is formed of several alternating
layers of plastic (polymer) and fabric. In such a composite
structure, the materials synergistically complement each other by
providing characteristics unavailable from the other material, and
by providing a structure with characteristics better than either
material alone In the case of sleeves for microwave vessels, the
plastic portions of such a vessel offer chemical resistance and
structural strength. The fabric portions offer additional strength
as well as flexibility and the ability to change shape without
breaking or shattering. Accordingly, when plastic-fabric composite
vessels fail under pressure, they tend to fail rather gently.
Stated differently, a fabric vessel, even if it could be
constructed to hold gases, would never offer the strength required
for high-pressure conditions. Alternatively, engineering resins and
other materials can withstand high pressures, but tend to fail by
shattering. When used together in a composite structure, however,
the combination provides the strength for maintaining a high
pressure in the vessel, while preventing shattering should the
plastic fail.
[0006] Versions of such composite fabric vessels are disclosed, for
example, in U.S. Pat. Nos. 5,427,741 and 5,520,886, both of which
are commonly assigned with the present invention. Another version
is set forth in co-pending and commonly assigned application Ser.
No. 09/062,858, filed Apr. 20, 1998, the contents of which are
incorporated entirely herein by reference ("the '858
application").
[0007] As composite pressure vessels have become more widely used
because of their advantages, certain characteristics have become
more evident that can be improved upon. In particular, and taking
for example the vessel structure illustrated in the co-pending '858
application, the flexible nature of the woven fabric layers tends
to be such that if the vessel is exposed to high pressure, it may
distort slightly. The vessel's characteristics are such that it
will stay distorted even after the pressure is removed or released.
By "distorted," it will be understood that only a very slight
change of shape may have taken place, sometimes as little as 0.001
inch. Nevertheless, when dealing with gases, such a change in
dimension is enough to prevent the vessel from maintaining an
effective seal under high pressure.
[0008] Additionally, in the vessel illustrated in the '858
application, the lid for the reaction portion of the vessel is
sealed to the top of the vessel using a flat surface-flat surface
contact arrangement (e.g., FIGS. 2 and 4 thereof). As in the case
of slight flexing of the composite sleeve, slight deviations from
the flat-on-flat contact can allow gases to escape. In some cases
such self-venting is desirable and helps keep a reaction at or
within desired pressure limits. In other cases, however, unintended
venting can release gases (including reagents) and prevent the
intended reaction from taking place.
[0009] Accordingly, a need exists for pressure vessels that
incorporate the advantages of protective composite sleeves, but
that improve upon the characteristics of the present vessels and
reduce the possibility for distortion or leakage.
OBJECT AND SUMMARY OF THE INVENTION
[0010] Therefore, it is an object of the present invention to
provide an improved vessel for high-pressure microwave assisted
chemistry that takes advantage of the characteristics of composite
materials and yet improves upon the existing structures.
[0011] The invention meets this object with a protective composite
sleeve for a microwave transparent vessel. The sleeve comprises a
microwave transparent inner cylindrical polymeric layer, a first
microwave transparent wound layer adjacent to and concentric with
the inner polymeric layer, and in which the winding is selected
from the group consisting of filaments and yarns. A microwave
transparent outer polymeric layer completes the basic sleeve
structure.
[0012] In another aspect, the invention comprises the composite
material from which the sleeve is made.
[0013] In yet another aspect, the invention comprises a pressure
vessel assembly for microwave assisted chemistry that incorporates
the composite sleeve.
[0014] These and other objects of the invention and the manner in
which they are accomplished will be more clearly understood when
taken in conjunction with the detailed description and the
accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective view of an embodiment of a pressure
vessel for microwave assisted chemistry according to the present
invention;
[0016] FIG. 2 is a cross-sectional view of the vessel and its frame
taken along lines 2-2 of FIG. 1;
[0017] FIG. 3 is an enlarged exploded partial view of the inner
liner and lid portions of the vessel according to the present
invention;
[0018] FIG. 4 is an exploded perspective view of the composite
sleeve according to the present invention, the vessel liner, and
its lid;
[0019] FIG. 5 is a partially cut-away perspective view of a
composite sleeve according to the present invention; and
[0020] FIG. 6 is a cross-sectional view taken along lines 6-6 of
FIG. 5 and illustrating the composite material used to form the
sleeve.
DETAILED DESCRIPTION
[0021] The present invention is a self-sealing vessel assembly for
high-pressure microwave assisted chemistry that is illustrated in
perspective view at 10 in FIG. 1. The vessel assembly 10 includes a
protective composite sleeve 11 that is also illustrated in more
detail in FIGS. 4, 5, and 6. The sleeve surrounds a microwave
transparent polymeric reaction cylinder 12 (e.g., FIGS. 3 and 4)
and a circular polymeric cap 13 for the cylinder 12. It will be
understood that although the invention herein is described in terms
of cylindrical vessels and sleeves, and that such are typically
most preferred and convenient for manufacture and use, other shapes
such as polygons could be used provided they otherwise offer the
structural integrity of a cylinder.
[0022] The vessel assembly 10 further includes a frame 14 into
which the composite sleeve 11, the reaction cylinder 12, and the
cap 13 fit along with a structural support disc 15 that is included
for strength purposes so that the reaction cylinder 12 can be
tailored for chemical inertness rather than strength. The frame 14
includes a threaded opening 16 (FIG. 2) that receives a bolt 17
that can be tightened down against the cap 13. In use, the bolt 17
helps secure the cap 13 at lower pressures while the cap itself
helps secure the opening with a self-sealing mechanism at higher
pressures as will be explained in more detail herein. For higher
pressure operation, the cap 13 and bolt 17 are often used in
combination with a structural disk (not shown) that adds additional
strength to the cap 13, the material for which is typically chosen
for chemical resistance.
[0023] As set forth in the '858 application incorporated above, one
purpose of the frame 14 is to maintain the vessel under seal at
certain pressures, while allowing the vessel to vent (as the frame
flexes) at other (higher) pressures. The design and materials for
the frame are accordingly selected for this purpose.
[0024] As illustrated in FIGS. 2, 3, and 4, the reaction cylinder
12 is closed at its lower end and open at the other end to receive
the cap 13. The open end of the cylinder 12 comprises a lip 20 that
is beveled inwardly from the open end and the cap 13 has a beveled
lower edge 21 that engages the beveled lip 20 when the cap 13 is
placed on the cylinder 12. In certain embodiments, the cap 13
further comprises a choke cylinder 22 that depends from the beveled
lower edge 21. The choke cylinder 22 has an outer diameter
substantially the same as the inner diameter of the polymeric
cylinder 12 so that the choke 22 provides a self-sealing mechanism
for the cylinder 12 as pressure from a microwave assisted chemical
reaction increases within the cylinder 12. The use of the bolt 17
against the cap 13 together with the choke cylinder 22 keeps the
reaction cylinder 12 sealed at both low and high pressures. The
bolt 17 keeps the cap secured at lower pressures, while at higher
pressures, the pressure exerted by a gas against the inner walls of
the depending choke cylinder 22 urges them against the inner
circumference of the reaction vessel 12 in a manner that seals the
vessel quite efficiently at the intended pressures.
[0025] In other embodiments, and as set forth in the '858
application, the choke cylinder 22 is omitted. In these
embodiments, the frame is designed to flex at certain pressures so
that the cap 13 will briefly disengage from the vessel 12 at such
pressures. In this manner the assembly releases pressure and then
immediately re-seals itself as the frame returns to it original
orientation against the vessel 12 and cap 13. As noted above, the
structural design of the frame can be selected to determine the
pressure at which the frame will allow the cap to open.
[0026] The reaction cylinder 12 and cap 13, along with all of the
other materials in the vessel assembly 10, are formed of a
microwave transparent materials, and in preferred embodiments, the
reaction cylinder 12 and the cap 13 are formed of polymerized
fluorinated hydrocarbons such as polytetrafluoroethylene, which is
commonly available under the trade name TEFLON.RTM..
[0027] Those familiar with polymers that are microwave transparent,
chemically inert, and structurally appropriate will recognize that
other polymers meeting these characteristics can be used for the
vessel and cap and can be selected without undue experimentation.
Exemplary fluoropolymers and other materials are also described in
U.S. Pat. No. 5,520,886, at column 5, lines 17-55. The contents of
U.S. Pat. No. 5,520,886 are incorporated entirely herein by
reference.
[0028] As illustrated in FIGS. 1 and 2, the supporting frame 14
extends along the length of the reaction cylinder 12 and the
composite sleeve 11 and then across the lid 13 as well as across
the closed end of the cylinder for preventing the lid 13 from being
displaced from the cylinder until the pressure generated inside the
vessel reaches the desired release point.
[0029] The beveled lip 20 of the reaction cylinder and the beveled
edge 21 of the cap 13 form a much more efficient seal in vessel
systems of this type than do flat surfaces that simply bear against
one another in planar fashion. The use of the beveled lip 20 and
beveled edge 21 greatly increases the surface contact area between
the lid 13 and the reaction cylinder 12 thus providing a more
efficient seal under the various stresses that the overall vessel
assembly experiences as gas pressure increases within the cylinder
12.
[0030] Furthermore, the structural stability provided by the
improved composite sleeve makes the beveled choke cap 13 much more
effective than it would be otherwise, as well as increasing its
durability.
[0031] In preferred embodiments, the composite sleeve 11 comprises
a microwave transparent inner cylindrical polymeric layer 23, a
first microwave transparent wound layer 24 adjacent to and
concentric with the inner polymer layer 23 in which the winding
(FIG. 5) is selected from the group consisting of filaments and
yarns, and a microwave transparent outer polymeric layer 25.
[0032] It has been discovered, according to the present invention,
that incorporating at least one (and possibly several) textile
layers in which the filaments or yarns are wound rather than woven,
knitted, or nonwoven, maintains the structural integrity of the
sleeve 11 for many more cycles of operation than has been the case
with composite sleeves in which the fabric layers have been, for
example, woven. In particular, it has been discovered if the
windings are made under tension, they form a particularly strong
structural geometry that remains unaffected even under exposure to
high pressure. This appears to result from the windings being
directly circumferential to the radial forces inside the reaction
vessel 12 and transmitted therethrough to the sleeve 11 as gases
exert pressure against the inner cylinder 12. As used herein, the
term "textile" includes fiber, filaments, yarns, and fabrics; e.g.,
Hoechst Celanese Dictionary of Fiber & Textile Technology (1990
Hoechst Celanese Corporation) at page 157. Thus, the would layers
of filaments or yarns described herein are properly referred to as
textile layers, as are the layers of woven, nonwoven, knitted, or
braided fabric.
[0033] In order to obtain the strength advantages generally
required under pressure, the composite sleeve 11 preferably further
comprises at least one structural polymer layer 26 between the
wound layer 24 and the outer polymer layer 25. In preferred
embodiments, the structural polymer layer 26 is an engineering
resin, with materials such as polyimides being most preferred. By
comparison, the inner layer 23 and outer layers 25 are typically
selected for chemical inertness and are often formed of
polytetrafluoroethylene or some other generally inert polymeric
material. Appropriate engineering resins are well known to those of
ordinary skill in these arts and can be selected and manufactured
without undue experimentation. Exemplary resins are described at
column 6, lines 10-40 of U.S. Pat. No. 5,520,886, or in Lewis,
Hawley's Condensed Chemical Dictionary, 12.sup.th Edition at pages
464-65 ("engineering material").
[0034] As FIG. 6 illustrates, in the most preferred embodiments,
the composite sleeve 11 further comprises a plurality of pairs of
adjacent concentric layers of structural polymer and fabric in
addition to the wound layer 24 and the outer polymer layer 25. FIG.
6 illustrates three additional fabric layers 27, 30, and 31 and two
additional layers 32 and 33 of the preferred engineering resin.
[0035] It will be understood that the fabric layers 27, 30, and 31
can also be wound in the same manner as the layer 24, or
alternatively, because of the strength advantages provided by even
one wound layer, the additional fabric layers can comprise the
woven, nonwoven, braided, or knitted fabrics previously used in
such composite sleeves. Thus, at least one, possibly several, and
potentially all of the fabric layers can be wound.
[0036] Although the illustrated embodiment shows the wound layer 24
as the innermost textile layer, it will be understood that if a
single wound layer is incorporated, it can comprise the innermost
textile layer, the outermost textile layer, or any one or more
layers in between. Furthermore, textile layers can be positioned
directly adjacent one another, including wound layers on wound
layers, and (in a particularly preferred embodiment) wound layers
on woven (or other fabric) layers.
[0037] The windings used to make the layer 24 are selected from the
group consisting of filaments and yarns, with TEFLON.RTM.-coated
fiberglass yarns being presently most preferred. Other yarns or
filaments can also be used provided they have the required
characteristics of microwave transparency, chemical inertness, and
appropriate strength.
[0038] Accordingly, in another aspect, the invention comprises the
protective composite sleeve material itself which comprises the
microwave transparent wound fabric layer fixed with the microwave
transparent structural medium with the wound layer being selected
from the group consisting of filaments and yarns. As in the
previous embodiments, the structural medium is preferably a first
polymer, preferably an engineering resin such as a polyimide. The
inner and outer layers are selected for chemical inertness and
preferably comprise polytetrafluoroethylene. The material can
include as many pairs of additional structural polymers and
additional structural textile layers as may be desired or necessary
with a total of four or five textile layers (including the wound
layer) being most preferred.
[0039] The composite sleeve illustrated in FIGS. 5 and 6 can be
formed in any manner suitable to achieve the final structure, one
example of which will be described herein. In a preferred
technique, TEFLON.RTM. tape is wrapped on a mandrel (preferably one
of surface-hardened aluminum) having a diameter the same as the
desired inner diameter of the composite sleeve. When properly
wound, the TEFLON.RTM. tape forms a cylinder over the mandrel.
[0040] In a next step, the yarn or filament is wound over the
TEFLON.RTM. tape under tension, and with the filaments or yarns
closely adjacent one another. The yarn can be wound in single or
multiple passes (i.e., to form wound-on-wound layers) depending
upon the desired end structure. The yarn layer is then wound (i.e.,
covered) with a tape of the desired engineering resin.
[0041] Next, in presently preferred embodiments, a woven fiberglass
fabric is added as a sock over the layer of engineering resin tape
on the mandrel. Before being added, the fiberglass sock is
heat-treated, typically using a microwave technique, to remove any
carbon or other impurities that would be responsive to microwave
radiation in the final composite sleeve. As noted above, the
successive fabric layers could alternatively be wound rather than
woven just like the first fabric layer.
[0042] Furthermore, if desired, two or more wound layers can be
adjacent one another, or a wound layer can be adjacent a woven (or
other fabric) layer without any polymer layer therebetween.
[0043] Additional layers of engineering resin tape and fabric or
windings are added in the same manner to obtain the desired number
of layers of each.
[0044] In the next-to-last step, another layer of TEFLON.RTM. tape
is wound over the outermost layer of fabric. As a final winding
step, a heat-shrinkable tape is wound over the outermost coating of
the cylinder precursor materials on the mandrel. The mandrel and
the wound and sock type layers are then heated to an appropriate
temperature (325.degree. C. for about 40 minutes in preferred
embodiments) to melt the resins. At the same time the tape shrinks
under the influence of heat thus applying a compressive force to
the entire structure which gives it additional structural
strength.
[0045] After the heating step, the mandrels and surrounding
materials are allowed to cool after which the sleeves are removed
from the mandrel and cut into appropriate lengths for use with the
vessels described herein.
[0046] As recognized by those who use microwave assisted chemistry
on a regular basis, the vessel assemblies described herein are
typically, and in many cases preferably, used in systems for
microwave assisted chemistry that comprise a source of microwave
radiation, a cavity (resonator) in microwave communication with the
source, and a plurality of the reaction vessels of the type
described herein in the cavity. In many cases, the vessels are
placed upon a reciprocating turntable that helps move the vessels
slightly through the microwave pattern that becomes established in
the cavity. Magnetrons are typically used as sources for such
devices because of their availability, reliability, and cost
effectiveness. Other sources such as klystrons, solid-state
sources, or switching power supplies (converters or inverters) can
also be incorporated as is described, for example, in co-pending
and commonly assigned patent application Ser. No. 09/063,545, filed
Apr. 21, 1998, for "Use of Continuously Variable Power in Microwave
Assisted Chemistry."
[0047] In the drawings and specification, there have been disclosed
typical embodiments of the invention, and, although specific terms
have been employed, they have been used in a generic and
descriptive sense only and not for purposes of limitation, the
scope of the invention being set forth in the following claims.
* * * * *